Mercruiser 3.0LX Acceleration Problem

[MH9371B]

Engine is a 1995 Mercruiser 3.0LX

Recently I had my '95 Sea Ray 195BR out on the water and when I opened the throttle wide, the engine would only get up to about 3000 RPM, then slowly creep to about 3900 RPM as the boat tried to get up on plane. Then, even with throttle wide open, would never get above that. This was only with me onboard so I'm sure it would be worse with passengers.

When I got it home, I put it on muffs and did not have this problem at all, so it only happens when it's in the water.

I suspected it might be bad gas, as it still had some fuel in the tank from last season, so I ran some Sea Foam gas treatment through it, and still had the same problem.

Spark plugs are brand new, as well.

Any ideas?

 

[81 Checkmate]

Re: Mercruiser 3.0LX Acceleration Problem

Is this the first time in this boat? Did it do this last year? How does it run? Good, Bad, Ugly? Could be the way you are triming the out drive.

 

[egleas84]

Re: Mercruiser 3.0LX Acceleration Problem

I'm having the EXACT same problem with my 1983 Mercruiser 120 3.0L in Stingray SVB165.

I dumped my tank and put all new gas and added Seafoam; gave me a little more umph on the hole shot, but not much planes fine with just me on it, with 2+ its boggy. I'm getting much better RPM's than you too... (~4400 when it gets up on plane, finally).

I've seen some discussion that cleaning/replacing clogged carb jets and getting a bigger bore on the accellerator jet helps in some other posts.

I start with my trim all the way down and then bring it up slowly as it gets on plane and accellerates.

What's your prop pitch?

 

[MH9371B]

Re: Mercruiser 3.0LX Acceleration Problem

No, I've had this boat for 8 years and this is the first time it has happened, so I doubt it is anything prop or trim related.

 

[Bondo]

Re: Mercruiser 3.0LX Acceleration Problem

No, I've had this boat for 8 years

Ayuh,... So how long ago was it given a Complete Tune Up, 'n Full Servicing,..??

 

[MH9371B]

Re: Mercruiser 3.0LX Acceleration Problem

I do most of the tune-up work myself. I just finished talking to a mech. at the boat shop I normally go to, and he suggested giving the carb a full cleaning (not just spraying carb cleaner, but actually taking it off and having it completely cleaned).

 

[egleas84]

Re: Mercruiser 3.0LX Acceleration Problem

I do most of the tune-up work myself. I just finished talking to a mech. at the boat shop I normally go to, and he suggested giving the carb a full cleaning (not just spraying carb cleaner, but actually taking it off and having it completely cleaned).

It was suggested by other members that I do the same. The difference is I have no idea what I'm doing. Interesting to see if that solves it (then I'll do mine). Could an auto shop clean it?

 

[Bondo]

Re: Mercruiser 3.0LX Acceleration Problem

It was suggested by other members that I do the same. The difference is I have no idea what I'm doing. Interesting to see if that solves it (then I'll do mine). Could an auto shop clean it?

Ayuh,... I guess that would depend on Which shop...

Carbs haven't been used on cars in 20 years...

 

[egleas84]

Re: Mercruiser 3.0LX Acceleration Problem

Ayuh,... I guess that would depend on Which shop...

Carbs haven't been used on cars in 20 years...

I called some marine guys to compare... They said that the "accelerator pump" is likely bad and that a rebuild kit would solve it.

Sounds like the rebuild is the way to go then!

 

[fishrdan]

Re: Mercruiser 3.0LX Acceleration Problem

They said that the "accelerator pump" is likely bad.................. and that a rebuild kit would solve it.

A bad accelerator pump will cause problems while opening the throttle, not holding the throttle in position, steady. From the comments made, it does not sound like an accelerator pump problem. With the engine off and the flame arrestor removed, look down the carb while someone else advances the throttle from idle to WOT, you should see a steady stream of fuel shoot out the accelerator pump discharge tubes, 2 streams.

That said, the carb could still need rebuilding.

If you suspect bad fuel, run the boat off a different fuel source (outboard fuel tank) to see if the problem goes away.

 

[EMC 1810SS]

Re: Mercruiser 3.0LX Acceleration Problem

Have you tried changing the water seperating fuel filter? It may be full of water.

I would also check the rotor, cap and wires if they havent been replaced recently. It sounds like a lack of fuel or spark to me......

 

[fat fanny]

Re: Mercruiser 3.0LX Acceleration Problem

I have basically the same set up as you just a foot shorter and have bnever experienced this exact issue but! Listen to what Bond-o said a complete servicing Drain old fuel clean and check pick up tube and screen at it's bottom make sure the anti siphon valve is functioning blow out the vent line from the tank change and clean the fuel filters (one on pum and one in the carb) teat fuel pressure from the pump to OEM specs tear down and rebuild carb (soak,clean and blow it out completely) change all perishables plugs,wires,fluids and filters and then go through all electrical connections clean lube and tighten then perform the factory trouble shooting on all ignition components and re-fill with frash fuel. Having a Merc service manual is priceless Thanx Don S and don't forget to do a compression test on all 4 cylinders. Hope this helps.

 

[egleas84]

Re: Mercruiser 3.0LX Acceleration Problem

Testing tomorrow after full tune up, carb rebuild, and even a new Mercury prop (mine was some POS that didn't match the boat/power package that po put on).

Ill Let you know if my acceleration problem is gone

 

[JaseBosto]

Re: Mercruiser 3.0LX Acceleration Problem

run a compression test.....

 

[egleas84]

Re: Mercruiser 3.0LX Acceleration Problem

Not sure what the OP's case is but my comp is good. Getting over 4400 RPM's. Was checked and was fine last year.

 

[MH9371B]

Re: Mercruiser 3.0LX Acceleration Problem

Had carb rebuilt and waiting to get it out on the water to test. Will let you know results!

 

[egleas84]

Re: Mercruiser 3.0LX Acceleration Problem

Mine's solved with the tuneup and carb rebuild. I threw a new prop on it too, but it was the same diameter and pitch.

 

[MH9371B]

Re: Mercruiser 3.0LX Acceleration Problem

I haven't had the chance to test mine yet because after my carb rebuild, I can't get the engine to stay in idle. I don't know if I'm not adjusting it right, or if the place didn't do a good rebuild.

 

[MH9371B]

Re: Mercruiser 3.0LX Acceleration Problem

Update:

Had boat in water today after I got the idleing problem squared away.

Same symptoms as my original post. I've had carb rebuilt and changed out filter in fuel pump as well as inlet filter going into carb.

One thing I did not put in my original post, is that the engine makes a pretty good sputtering noise when it is at WOT which does not go away until you bring it back to idle.

Anyone have any ideas?

 

[75TowerOfPower]

Re: Mercruiser 3.0LX Acceleration Problem

Have you done a tune up recently?

Sounds like not burning all the fuel or not burning fuel at all in one of the cylinders.